Search

In this study, experiments were performed to find out how the thermal performance of a two-phase thermosyphon solar collector was affected by using different refrigerants. Three identical small-scale solar water heating systems, using refrigerants R-134a, R407C, and R410A, were constructed and tested side-by-side under various environmental and load conditions. The performance of the system under clear-sky conditions has been investigated with and without water load. Detailed temperature distributions and cumulative collection efficiencies were determined and presented. The experimental results were compared to the results found in the literature and they showed good agreement. Keywords: Phase-change; Heat-pipe solar collector; Refrigerant-charged solar collector; Solar water heating

A solar cooking system using vacuum-tube collectors with heat pipes containing a refrigerant as working fluid has been fabricated, and its performance has been analysed experimentally. The experiments were conducted during clear days in July and August of 2002 in Elazig, Turkey under similar meteorological conditions for three refrigerants and water. Detailed temperature distributions and their time dependences were measured. The maximum temperature obtained in a pot containing 71 of edible oil was 175[degrees]C. Also, the cooker was successfully used to cook several foods. The cooking processes were performed with the cooker in 27-70 min periods. Keywords: Solar cooker; Vacuum-tube collector; Heat pipe; Refrigerant

The cylindrical latent heat storage tanks considered here are part of a domestic heating system. In this study, the performances of such energy storage tanks are optimized theoretically. Two different models describing the diurnal transient behaviour of the phase change unit were used. The first is suited to tanks where the phase change material (PCM) is packed in cylinders and the heat transfer fluid (HTF) flows parallel to it (mode 1). The second is suited to tanks where pipes containing the fluid are embedded in the PCM (mode 2). The problem (treated as two-dimensional) is tackled with an enthalpy-based method coupled to the convective heat transfer from the HTF. A series of numerical tests are then undertaken to assess the effects of various PCMs, cylinder radii, pipe radii, total PCM volume in the tank, mass flow rates of fluid, and inlet temperatures of the HTF on the storing time. In addition, optimal geometric design of the store depending on these parameters and PCMs is presented.